The present invention relates to coin validators and in particular, relates to coin validators having an eddy-current sensor for measuring of magnetic features of coins as they pass the sensor.
A primary magnetic field produces eddy-currents in the coin being evaluated and a determination of the authenticity and denomination of the coin is completed. A disturbance of the primary magnetic field caused by the eddy-currents produces a sensor signal. The eddy-currents (and so the signal) depend on such individual features of coin s its shape, specific conductivity and permeance of the material which the coin is made with. More information about the properties of the coin by using several frequencies.
With the sensor of the present invention, information is obtained as the coin moves past the sensor. The output signal of the sensor depends on the position of the coin relative to the sensors, the shape of the coin, and the shape of the primary magnetic field. To make the dependence more distinct for different positions as the coin is moving past the sensor, the magnetic field is oblate in shape.
A coin validator according to the present invention comprises a pathway for guiding a coin as it moves past any eddy-current sensor. The eddy-current sensor evaluates the shape of the coin, the specific conductivity of the coin, and permeance of the coin.
Based on these evaluations, a prediction of the coin""s denomination and authenticity is made.
The sensor includes a thin rectangle ferrite plate with a primary coil and a sensing coil. The primary coil is a short cylindrical coil placed centrally on one side of the plate with the axis of the coil perpendicular to the plate""s surface. This coil generates a primary magnetic field and is a field coil. The sensing coil is wound around opposite ends of the ferrite plate and has the major axis of the coil along the plate. The sensing coil is symmetrical about the middle of the plate. It produces a signal that is the sensor""s response. The sensor has a plane of symmetry passing through the middle of the plate and perpendicular to the largest surface of the plate.
According to an aspect of the invention, the field coil has a cylindrical compact winding, its diameter is equal to the width of the largest surface of the ferrite plate, and the sensing coil has two symmetrical halves placed between the ends of the plate and the field coil.
According to a further aspect of the invention, setting of the sensor in the pathway is carried out in such a manner that the perpendicular to the plane of symmetry and direction of the coin moving makes an angle of about 45 degrees.
According to yet a further aspect of the invention, the guide of the pathway near the sensor is curvilinear.